This invention relates to a holding device for surface sheets or surface plates in a press intended for pressing wood fibre products, the said device comprising a press plate, a source for supplying vacuum to the side of a surface sheet or surface plate which faces towards the press plate, a vacuum-distributing body placed between the press plate and the surface sheet, and a seal which is arranged to afford sealing between the press plate and the surface sheet.
Devices for holding surface sheets in a press by means of vacuum are already known, one such device being shown in German patent specification No. 829,793. Shown in Swedish Pat. No. 328,695 is a further apparatus wherein a solid plate is used as a spacing member and a vacuum operates mainly around the surface plate in the vicinity of its edge.
In addition it has also long been known how to utilize for example a so-called compensation wire in order to compensate for sundry irregularities which can appear in a press. One example of such a wire is disclosed in Swedish Pat. No. 152,766.
Swedish patent application No. 7412003-1 discloses how the wire can be given an additional task apart from compensating for irregularities, namely it can also be used to reliably distribute the vacuum generated in order to hold the surface plate over its entire surface.
In applicants own earlier design according to the aforesaid Swedish patent application No. 7412003-1 and in other prior art mechanical designs to hold a surface plate and wire it was necessary to remove both the surface plate and the compensation wire in order to change the surface plate. In view of the fact that both compensation wires and surface plates have large dimensions and are thus both heavy and difficult to handle it would be a great advantage if the surface plate could be removed without it being necessary to remove anything else. The object of the present invention is therefore to provide such a device in which only the surface plate needs to be removed from the plate when changing the surface plate.